Injection molding machine

ABSTRACT

Provided is an injection molding machine using a built-in type motor as a measuring electric servomotor. In order to reduce the entire length of the machine (the injection molding machine), the metering electric motor is exemplified by a hollow built-in type motor, which includes a cylindrical stator, and a cylindrical rotor positioned in the stator. A sleeve is fixed in the rotor of the built-in type motor, and a member fixing the rear end portion of a screw and the sleeve are connected/fixed. Moreover, a nut member as a straight portion of a ball screw mechanism for converting the rotation of an injecting electric motor into linear motions and the sleeve are connected/fixed.

TECHNICAL FIELD

The present invention relates to an in-line screw type injection moldingmachine of an electrically driven type, and particularly relates to aninjection molding machine using a built-in type motor as a meteringelectric servomotor.

BACKGROUND ART

For example, many in-line screw type injection molding machines ofelectrically driven types according to the background art use thefollowing configuration. That is, a timing belt is extended between adriving pulley fixed to an output shaft of a metering electric motor anda driven pulley formed integrally with or fixed to a rotary connector towhich a base end portion of a screw is fixed. Rotation of the meteringelectric motor is transmitted through a rotation transmitting mechanismconstituted by the pulleys and the belt to the rotary connector retainedrotatably on a linear motion block to be driven linearly by a drivingforce of an injecting electric motor. Thus, the screw integrated withthe rotary connector can be rotated. When such a configuration is used,a general AC servomotor having an output shaft in its center can be usedas the metering electric motor. However, a reduction mechanism has to bebuilt by the rotation transmitting mechanism constituted by the pulleysand the belt. Thus, the number of parts increases to hinder space savingof the machine. In addition, since it is necessary to rotate the drivenpulley whose diameter is comparatively large, the rotational inertiaincreases to limit the improvement of the transient response performanceof rotation transmission unavoidably.

An injection molding machine using an internally hollow built-in typemotor (direct coupling type motor) as the metering electric motor inorder to reduce the rotational inertia to thereby improve the transientresponse performance of rotation transmission has been known, forexample, in JP-A-08-039631 (Patent Document 1). The background-arttechnique in Patent Document 1 discloses a configuration in which aspline shaft formed integrally with a screw is spline-connected directlyto a rotor of a built-in type motor as a metering electric servomotor soas to make the built-in type motor drive and rotate the screw. Accordingto the invention proposed in Patent Document 1, there is provided asingle built-in type motor serving as both a metering electric motor andan injecting electric servomotor, in which a ball screw or a splineshaft portion of a ball screw/spline shaft unit integrated with thescrew is alternatively selected and rotated by a clutch so that thescrew can be alternatively selectively rotated or moved linearly.

In the background-art technique in Patent Document 1, however, the ballscrew is formed behind the screw and the spline shaft is formed behindthe ball screw, so that the entire length of the machine becomes long.In addition, since the spline shaft is spline-connected to the rotor ofthe built-in type motor, constituent elements for the spline connectionare required to thereby result in labor increase for the attachment.

According to the invention proposed in Patent Document 1, a singlebuilt-in type motor serves as both the metering electric motor and theinjecting electric servomotor. It is therefore necessary to provide twoclutches and a spline shaft connection mechanism. Thus, there is aproblem that the structure is complicated and the assembly istroublesome. In addition, while the screw is rotated, axial pressurecannot be applied to the screw by the motor. Thus, there is anotherproblem that back pressure cannot be applied in a metering step.

In an injection molding machine using a built-in type motor as ametering electric servomotor, it can be therefore regarded as rationalthat a rotary connector fixing and holding a base end portion of a screwis fixed to a cylindrical rotor rotating inside a cylindrical stator soas to transmit rotation of the metering built-in type motor directly tothe screw and to thereby rotate the screw. In addition, it can beregarded as general that a linear motion portion of a ball screwmechanism for converting rotation of an injecting electric motor intolinear motion is connected and fixed to a linear motion block which ismounted with the metering built-in type motor and which movesforward/backward, so that the linear motion block is driven linearly bythe driving force of the injecting electric motor to thereby move thescrew linearly.

-   Patent Document 1: JP-A-08-039631

DISCLOSURE OF THE INVENTION Problem that the Invention is to Solve

As described above, the transient response performance at the time ofstarting up of screw rotation when metering is started can be enhancedby use of a built-in type motor as a metering electric motor. Inaddition, in the configuration where the linear motion portion of theball screw mechanism is connected and fixed to the linear motion blockwhich is mounted with the metering built-in type motor and which movesforward/backward, the linear motion portion of the ball screw mechanismdoes not rotate. It is therefore easy to control back pressure by theinjecting electric motor in a metering step.

However, in order to fix the linear motion portion of the ball screwmechanism, for example, a nut body to the linear motion block mountedwith the metering built-in type motor, it is necessary to provide aswelling portion or the like along the screw shaft in the linear motionblock. As a result, a portion protruding from the metering built-in typemotor is inevitably provided in the linear motion block so as to hinderthe request for shortening the entire length of the machine (injectionmolding machine).

The present invention was developed in consideration of theaforementioned problem. An object of the invention is to provide aninjection molding machine using a built-in type motor as a meteringelectric servomotor, in which the entire length of the machine(injection molding machine) can be shortened.

Means for Solving the Problem

In order to attain the aforementioned object, the invention provides anin-line screw type injection molding machine in which a screw in aheating cylinder is rotated to move a raw resin toward a forward end ofthe screw while kneading and plasticizing the raw resin, accumulate thethus molten resin on the forward end side of the screw after measurementof the molten resin, and move the screw forward to thereby inject andfill the molten resin into a mold. In the injection molding machine, aninternally hollow built-in type motor having a cylindrical stator and acylindrical rotor located inside the stator is used as a meteringelectric motor, a sleeve is fixed to the inside of the rotor of thebuilt-in type motor, and a member to which a rear end portion of thescrew is fixed is connected and fixed to the sleeve, while a nut body asa linear motion portion of a ball screw mechanism for convertingrotation of an injecting electric motor into linear motion is connectedand fixed to the sleeve.

EFFECT OF THE INVENTION

According to the present invention, a built-in type motor (meteringbuilt-in motor) is used as a metering electric servomotor, a sleeve isfixed to the inside of a rotor of the built-in type motor, and a member(rotary connector) to which a rear end portion of a screw is fixed isconnected and fixed to the sleeve, while a nut body as a linear motionportion of a ball screw mechanism for converting rotation of aninjecting electric motor into linear motion is connected and fixed tothe sleeve. That is, the nut body of the ball screw mechanism isconnected to the sleeve integrated with the rotor of the meteringbuilt-in motor. It is therefore possible to miniaturize a linear motionblock mounted with the metering built-in motor. In addition, the insideof the sleeve (the inside of the rotor of the metering built-in motor)can be effectively used as a space to mount the member (rotaryconnector) to which the rear end portion of the screw is fixed, and aspace to be entered by a screw shaft screwed to the nut body. Thisconfiguration can contribute to reduction in the entire length of themachine (injection molding machine). In addition, mounting is so simplethat the member (rotary connector) to which the rear end portion of thescrew is fixed and the nut body of the ball screw mechanism are fixed tothe sleeve fixed to the rotor of the metering built-in motor. Due tosuch simple mounting, the injection molding machine is also superior inmounting workability.

According to the present invention, however, the rotor of the meteringbuilt-in motor and the nut body of the ball screw mechanism (the linearmotion portion of the ball screw mechanism) are integrated. Therefore,when the screw rotates due to rotation of the metering built-in motor,the nut body of the ball screw mechanism also rotates. Due to therotation of the nut body caused by the rotation and drive of the screw,the nut body moves linearly along the screw shaft. Therefore, in themetering step, rotation of the metering built-in motor is controlledwhile rotation of the injecting electric motor is controlled to cancelthe linear motion of the nut body caused by the rotation of the nut bodydue to the rotation and drive of the screw.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below withreference to the drawings.

FIGS. 1 to 5 relate to an in-line screw type injection molding machineof an electrically driven type according to the embodiment of theinvention (hereinafter referred to as this embodiment). FIG. 1 is a mainportion sectional view showing the outline of an injection systemmechanism of the injection molding machine according to this embodiment.

In FIG. 1, the reference numeral 1 represents a head stock disposed on anot-shown injection unit base plate; 2, a holding plate disposed on thenot-shown injection unit base plate so as to be opposed to the headstock 1 at a predetermined distance therefrom; 3, a heating cylinderwhose rear end portion is fixed to the head stock 1; 4, a nozzleattached to a front end of the heating cylinder 3; 5, a band heaterwound around an outer circumference of the heating cylinder 3; 6, ascrew disposed in the heating cylinder 3 to be able to rotate and moveforward/backward; and 1 a and 3 a, raw resin supply holes provided inthe head stock 1 and the heating cylinder 3 respectively so that a rawresin dropping down and supplied from a not-shown hopper can be suppliedinto the rear end portion of the heating cylinder 3.

In addition, the reference numeral 7 represents a connector bar extendedbetween the head stock 1 and the holding plate 2; 8, a linear motionblock (linear motion body) provided on a not-shown rail member withinterposition of a linear motion guide, so as to be able to moveforward/backward between the head stock 1 and the holding plate 2; 9, aninternally hollow metering built-in type motor (hereinafter referred toas “metering built-in motor 9”) mounted on the linear motion block 8;10, a casing of the metering built-in motor 9; 11, a cylindrical statorof the metering built-in motor 9, which is fixed to the casing 10; 12, acylindrical rotor of the metering built-in motor 9, which can rotateinside the stator 11; 13, a sleeve fixed to an inner circumferentialsurface of the rotor 12 by strong fitting or the like; 14, a bearing putbetween the casing 10 and the sleeve 13 so as to support the sleeve 13rotatably; and 15, a rotary connector fixing a base end portion of thescrew 6 and fixed to the sleeve 13.

In addition, the reference numeral 16 represents an internally hollowinjecting built-in type motor (hereinafter referred to as injectingbuilt-in motor 16) mounted on the holding plate 2; 17, a casing of theinjecting built-in motor 16 which is fixed to the casing 17; 18, acylindrical stator of the injecting built-in motor 16; 19, a cylindricalrotor of the injecting built-in motor 16, which can rotate inside thestator 18; and 20, a sleeve fixed on an inner circumferential surface ofthe rotor 19 by strong fitting or the like. Though depicted simply inFIG. 1, the sleeve 20 is designed to be held rotatably in the casing 17with a not-shown bearing interposed therebetween.

In addition, the reference numeral 21 represents a ball screw mechanismfor converting rotation of the injecting built-in motor 16 into linearmotion; 22, a screw shaft of the ball screw mechanism 21 (a rotaryportion of the ball screw mechanism 21) held rotatably on the holdingplate 2 with a bearing 24 interposed therebetween; 23, a nut body of theball screw mechanism 21 (a linear motion portion of the ball screwmechanism 21) which is screwed to the screw shaft 22 to make linearmotion along the screw shaft 22 due to rotation of the screw shaft 22and whose end portion is fixed to the sleeve 13 of the metering built-inmotor 9 side directly or through a suitable member; and 25, a connectorfor connecting and fixing the sleeve 20 of the injecting built-in motor16 side and an end portion of the screw shaft 22.

In this embodiment, the screw lead of the screw shaft 22 of the ballscrew mechanism 21 driven and rotated directly by the rotor 19 of theinjecting built-in motor 16 is set to be 1.5 or more times as long asthe diameter of the screw 6. As a result, even in a configuration wherethe rotary portion of the ball screw mechanism 21 used for injecting isdriven directly by a motor, the injection performance can be securedsufficiently.

FIG. 2 is a main portion enlarged view showing a connecting/fixingportion between the sleeve 20 of the injecting built-in motor 16 sideand the end portion of the screw shaft 22 of the ball screw mechanism21. As shown in FIG. 2, the connector 25 is put between an innercircumferential surface of the sleeve 20 and an outer circumferentialsurface of the end portion of the screw shaft 22. An undermentionedouter race 26 of the connector 25 is brought into pressure contact withthe inner circumferential surface of the sleeve 20, while anundermentioned inner race 27 of the connector 25 is brought intopressure contact with the outer circumferential surface of the endportion of the screw shaft 22. Thus, the sleeve 20 and the screw shaft22 are firmly fixed and integrated by the connector 25. The operation ofadjusting the pressure contact of the connector 25 can be performedeasily and surely by the operation of rotating each undermentionedadjustment screw 30 of the connector 25. The operation of rotating theadjustment screw 30 is performed from a free end side of the hollowportion of the injecting built-in motor 16. Thus, the hollow portion ofthe injecting built-in motor 16 can be effectively used to improve thespace factor, while the connection and fixation between the rotor 19 ofthe injecting built-in motor 16 and a member (the screw shaft 22 of theball screw mechanism 21 in this case) to be driven and rotated by therotor 19 can be performed easily and surely with good operationality.

In addition, in this embodiment, as described above, a built-in typemotor (the injecting built-in motor 16) is used as the injecting motorfor driving and rotating the screw shaft 22 of the ball screw mechanism21, and the rotor 19 of the injecting built-in motor 16 and the screwshaft 22 are integrated without using a rotation transmitting mechanismof pulleys and a belt so that the injecting built-in motor 16 candirectly drive the screw shaft 22 of the ball screw mechanism 21. Thus,the rotational inertia of the rotation transmitting system used forinjecting can be reduced so that the transient response performance ofrotation transmission can be improved. In addition, a reductionmechanism can be eliminated from the rotation transmitting system usedfor injecting. Thus, the number of parts can be reduced. In additionthereto, a motor with low-rotation-speed and high-torque specificationscan be used as the injecting built-in motor 16, and the transientresponse performance of rotation transmission in the rotationtransmitting system used for injecting can be improved. Thus, it ispossible to obtain good forward starting characteristic of the screw 6at an initial stage of injection (primary injection).

FIG. 3 is a view showing a sectional structure of the connector 25. Theconnector 25 is a kind of friction type fastener. The connector 25 is atool for fixing and integrating the shaft outer circumference and thecylinder inner circumference. The connector 25 is a tool which canfirmly connect the shaft outer circumference and the cylinder innercircumference without applying any processing to the shaft outercircumference and the cylinder inner circumference. The connector 25 cansimplify the structure for the connection and fixation. The connector 25is constituted by an outer race (outer ring portion) 26 which has atapered portion on its inner circumferential surface side and which canbe displaced radially, an inner race (inner ring portion) 27 which has atapered portion on its outer circumferential surface side and which canbe displaced radially, a first tapering 28 and a second tapering 29which are located between the outer race 26 and the inner race 27 andwhich can move axially (in the left/right direction in FIG. 3), and aplurality of fastening bolts 30 which move the first tapering 28 and thesecond tapering 29 axially. For the first tapering 28, the fasteningbolts 30 are screwed to threaded holes formed in the first tapering 28,respectively. For the second tapering 29, the fastening bolts 30 areloosely inserted into clearance holes formed in the second tapering 29,respectively, and the head portions of the fastening bolts 30 abutagainst the second tapering 29.

When each fastening bolt 30 is rotated in a predetermined direction inthe configuration shown in FIG. 3, the first tapering 28 moves in theillustrated right direction, while the second tapering 29 moves in theillustrated left direction. As a result, the outer race 26 is deformedto expand while the inner race 27 is deformed to narrow. Thus, the outerface 26 is brought into pressure contact with the inner circumferentialsurface of the sleeve 20, and the inner race 27 is brought into pressurecontact with the outer circumferential surface of the end portion of thescrew shaft 22.

FIG. 4 is a main portion enlarged view showing the connecting/fixingportion among the sleeve 13 of the metering built-in motor 9 side, therotary connector 15 fixing and holding the base end portion of the screw6, and the nut body 23 of the ball screw mechanism 21. As shown in FIG.4, the nut body 23 of the ball screw mechanism 21 is fixed to the sleeve13 by an attaching bolt 31. Thus, the mounting structure on the nut body23 side for motion transmission of the ball screw mechanism 21 can beextremely simplified, and assembly thereof also becomes easy.

In addition, as shown in FIG. 4, the rotary connector 15 fixing andholding the base end portion of the screw 6 is fitted into the sleeve13, and the rotary connector 15 is fixed to the sleeve 13 by anattaching bolt 32. In this embodiment, as described above, a built-intype motor (the metering built-in motor 9) is used as the metering motorfor driving and rotating the screw 6. Thus, the sleeve 13 is fixed tothe inside of the rotor 12 of the metering built-in motor 9, the rotaryconnector 15 to which the rear end portion of the screw 6 is fixed isconnected and fixed to the sleeve 13, and the nut body 23 serving as thelinear motion portion of the ball screw mechanism 21 for converting therotation of the injecting built-in motor 16 into linear motion isconnected and fixed to the sleeve 13. That is, the nut body 23 of theball screw mechanism 21 is connected to the sleeve 13 integrated withthe rotor 12 of the metering built-in motor 9. It is therefore possibleto miniaturize the linear motion block 8 mounted with the meteringbuilt-in motor 9. In addition, the inside of the sleeve 13 (the insideof the rotor 12 of the metering built-in motor 9) can be effectivelyused as a space to mount the rotary connector 15, and a space to beentered by the screw shaft 22 screwed to the nut body 23. Thisconfiguration can contribute to reduction in the entire length of themachine (injection molding machine). Further, in this embodiment, abuilt-in type motor (the metering built-in motor 9) is used as themetering motor for driving and rotating the screw 6, and the rotor 12 ofthe metering built-in motor 9 and the screw 6 are integrated withoutusing a rotation transmitting mechanism of pulleys and a belt so thatthe metering built-in motor 9 can directly drive the screw 6. Thus, therotational inertia of the rotation transmitting system used for meteringcan be reduced so that the transient response performance of rotationtransmission can be improved. In addition, a reduction mechanism can beeliminated from the rotation transmitting system used for metering.Thus, the number of parts can be reduced. In addition thereto, a motorwith low-rotation-speed and high-torque specifications can be used asthe metering built-in motor 9, and the transient response performance ofrotation transmission in the rotation transmitting system used formetering can be improved. Thus, it is possible to obtain good rotationstarting characteristic of the screw 6 at an initial stage of metering.Even when a high-viscosity resin material is used, stable rotation ofthe screw 6 can be obtained in an early stage so as to contribute tomolding of a good product. Furthermore, the nut body 23 and the rotaryconnector 15 can be fixed to the sleeve 13 in an extremely simple mannerusing the attaching bolts 31 and 32. Thus, the injection molding machineis also excellent in mounting workability.

In this embodiment, in a metering step, the metering built-in motor 9 iscontrolled and driven by rotational velocity (number of revolutions)feedback control through an undermentioned servo driver 45-1 inaccordance with an instruction from an undermentioned system controller41 which administers control of the machine (injection molding machine)as a whole. Thus, the screw 6 rotates in a predetermined directionintegrally with the sleeve 13 and the rotary connector 15. In a typicalmetering operation, a raw resin supplied from a not-shown hopper to therear end side of the screw 6 through the raw resin supply holes 1 a and3 a is kneaded and plasticized due to the rotation of the screw 6 whilebeing moved forward by the screw feed operation of the screw 6. In thisembodiment, when the screw 6 rotates in a predetermined direction, thenut body 23 fixed to the sleeve 13 also rotates. Due to the rotation ofthe nut body 23 caused by the rotation and drive of the screw 6, the nutbody 23 makes linear motion along the screw shaft 22. Therefore, inorder to cancel the linear motion of the nut body 23 (linear motion ofthe metering built-in motor 9 or the screw 6) caused by the rotation ofthe nut body 23 due to the rotation and drive of the screw 6, the systemcontroller 41 controls and drives the injecting built-in motor 16through an undermentioned servo driver 45-2 by a pressure feedbackcontrol using a set back pressure as an intended value. Thus, the backpressure applied to the screw 6 is kept at a predetermined pressure,while the screw 6 is moved backward by proper control as the resinmolten thus is fed to the front end side of the screw 6. That is, forexample, when the metering built-in motor 9 is rotated at 10 revolutionsper unit time, the injecting built-in motor 16 is rotated at 9.9revolutions per unit time. By such control, the linear motion of the nut23 caused by the rotation of the nut body 23 due to the rotation anddrive of the screw 6 can be canceled while predetermined back pressurecan applied to the screw 6. Then, as soon as one shot of the moltenresin is accumulated on the front end side of the screw 6, the rotationand drive of the screw 6 by the metering built-in motor 9 is suspended.

On the other hand, in an injecting and filling step, at a suitabletiming after metering has been completed, the injecting built-in motor16 is controlled and driven by speed feedback control through theundermentioned servo driver 45-2 in accordance with an instruction fromthe undermentioned system controller 41. Thus, the rotation of theinjecting built-in motor 16 is converted into linear motion by the ballscrew mechanism 21. The linear motion is transmitted to the screw 6through the aforementioned linear motion transmitting system to drivethe screw 6 forward rapidly. Thus, the molten resin accumulated on thefront end side of the screw 6 is injected and filled into a cavity of anot-shown mold which has been clamped so that a primary injection stepis carried out. In a pressure holding step following the primaryinjection step, the injecting built-in motor 16 is controlled and drivenby pressure feedback control through the servo driver 45-2 in accordancewith an instruction from the system controller 41. Thus, a set holdingpressure is applied from the screw 6 to the resin in the not-shown mold.

FIG. 5 is a block diagram showing a simplified configuration of acontrol system of the injection molding machine according to thisembodiment. In FIG. 5, the reference numeral 41 represents a systemcontroller which administers control of the machine (injection moldingmachine) as a whole; 42, an input unit by which an operator performsvarious input operations; 43, a display unit for displaying images tothe operator in various display modes; 44, a sensor group consisting ofa large number of sensors (position sensors, speed sensors, pressuresensors, rotation amount sensors, temperature sensors, etc.) disposed inportions of the machine; and 45, a driver group consisting of a largenumber of drivers (motor drivers, heater drivers, etc.) for controllingand driving actuators (motors including the aforementioned motors 9 and16), heaters, etc. disposed in portions of the machine. The driver group45 includes the servo driver 45-1 for driving the metering built-inmotor 9 by feedback control, and the servo driver 45-2 for driving theinjecting built-in motor 16 by feedback control.

In addition, in the system controller 41, the reference numeral 46represents an operating condition setting storage portion; 47, ameasured value storage portion; 48, an operating process controlportion; and 49, a display processing portion.

Operating control conditions of steps (steps of mold closing (moldclamping), injecting, metering, mold opening, forward ejecting, andbackward ejecting) of a molding cycle inputted in advance are storedrewritably in the operating condition setting storage portion 46.Metering information (position information, speed information, pressureinformation, rotation angle information, rotation velocity (number ofrevolutions per unit time) information, temperature information, etc.)of portions of the machine are imported from the sensor group 44 or thelike in real time and stored in the measured value storage portion 47.The operating process control portion 48 controls and drives the drivergroup 45 to execute operations of the steps, based on operation controlprograms provided in advance for the steps and set values of operatingconditions of the steps stored in the operating condition settingstorage portion 46 and with reference to the metering information in themeasured value storage portion 47, status confirmation information fromeach portion or its own clocking information. The display processingportion 49 generates images in various display modes and displays theimages on the display unit 43, based on display processing programsprovided in advance and fixed data for display and, if necessary, withreference to the contents of the operating condition setting storageportion 46 or the measured value storage portion 47.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A main portion sectional view showing the outline of aninjection system mechanism of an injection molding machine according toan embodiment of the invention.

[FIG. 2] A main portion enlarged view showing a connecting/fixingportion between a sleeve of an injecting built-in motor side and an endportion of a screw shaft of a ball screw mechanism in the injectionmolding machine according to the embodiment of the invention.

[FIG. 3] An enlarged sectional view of a connector in FIG. 2.

[FIG. 4] A main portion enlarged view showing a connecting/fixingportion among a sleeve of a metering built-in motor side, a rotaryconnector fixing and holding a base end portion of a screw, and a nutbody of the ball screw mechanism in the injection molding machineaccording to the embodiment of the invention.

[FIG. 5] A block diagram showing a simplified configuration of a controlsystem of the injection molding machine according to the embodiment ofthe invention.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   1 head stock-   1 a raw resin supply hole-   2 holding plate-   3 heating cylinder-   3 a raw resin supply hole-   4 nozzle-   5 band heater-   6 screw-   7 connector bar-   8 linear motion block-   9 metering built-in type motor (metering built-in motor)-   10 casing-   11 stator-   12 rotor-   13 sleeve-   14 bearing-   15 rotary connector-   16 injecting built-in type motor(injecting built-in motor)-   17 casing-   18 stator-   19 rotor-   20 sleeve-   21 ball screw mechanism-   22 screw shaft (rotary portion of ball screw mechanism)-   23 nut body (linear motion portion of ball screw mechanism)-   24 bearing-   25 connector-   26 outer race-   27 inner race-   28 first tapering-   29 second tapering-   30 fastening bolt-   31 attaching bolt-   32 attaching bolt-   41 system controller-   42 input unit-   43 display unit-   44 sensor group-   45 driver group-   45-1 servo driver (for metering)-   45-2 servo driver (for injecting)-   46 operating condition setting storage portion-   47 measured value storage portion-   48 operating process control portion-   49 display processing portion

1. An in-line screw injection molding machine in which a screw in aheating cylinder is rotated to move a raw resin toward a forward end ofthe screw while kneading and plasticizing the raw resin, accumulate thethus molten resin on the forward end side of the screw after measurementof the molten resin, and move the screw forward to thereby inject andfill the molten resin into a mold, wherein: an internally hollowbuilt-in motor having a cylindrical stator and a cylindrical rotorlocated inside the stator is used as a metering electric motor, a sleeveis fixed to the inside of the rotor of the built-in motor, and a memberto which a rear end portion of the screw is fixed is connected and fixedby a first bolt to the sleeve, while a nut body as a linear motionportion of a ball screw mechanism for converting rotation of aninjecting electric motor into linear motion is connected and fixed witha second bolt to the sleeve.
 2. An injection molding machine accordingto claim 1, further comprising: a controller which controls rotation ofthe metering electric motor consisting of the built-in motor in ametering step while controlling rotation of the injecting electric motorso as to cancel linear motion of the nut body caused due to rotation ofthe nut body caused by rotation and drive of the screw.
 3. An injectionmolding machine according to claim 2, wherein the built-in motor is usedas the injecting electric motor, a sleeve fixed to the inside of a rotorof the built-in motor as the injecting electric motor is connected andfixed to a screw shaft as a rotary portion of the ball screw mechanism,and a screw lead of the screw shaft is set to be 1.5 or more times aslong as a diameter of the screw.